XVIth International Workshop on
Quantum Systems in
Chemistry and Physics
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Bonding in negative ions:
The role of d orbitals of third period or heavier atom
Balázs Hajgató,1 Frank De Proft,1 David J. Tozer, 2 Paul Geerlings,1 and László Nyulászi3

1Eenheid Algemene Chemie (ALGC), Member of the QCMM Research Group – Alliance Ghent-Brussels, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium
2Department of Chemistry, University of Durham, South Road, Durham, DH1 3LE UK.
3Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Gellért tér 4, H–1521, Budapest, Hungary; Materials Structure and Modeling Research Group of the Hungarian Academy of Sciences, Budapest University of Technology and Economics, Szt. Gellért tér 4., Budapest, H-1111, Hungary
In the early 90's it has been shown that d-orbitals do not participate in the bonding of neutral molecules containing heavy atoms [1]. This founding is in agreement with the ionization energies of the pyridine-stibabenzene series obtained by photoelectron spectroscopy, where the A2 ionized states have almost constant energy within the series [2]. Since the a2 orbitals have two planar nodes through the heteroatom, they are relatively unperturbed by the heteroatom, and a d-orbital interaction would stabilize an A2 cationic state. In contrast to this, the electron transmission investigation of the electron affinities of the same series [3] revealed that A2 π* anionic state of phosphabenzene is stabilized by about 0.5 eV with respect to pyridine, while it remains almost constant for arsabenzene and stibabenzene, i.e., in all those compounds where the heteroatom have d-orbitals in the valence shell.
We have investigated the d-orbital contribution in the semi-occupied molecular orbitals of the pyridine-stibabenzene and furan-tellurophene series in both low-lying 2A2 and 2B1 anionic states by means of a newly developed, "potential wall confinement" technique [4]. We found a significantly increase in the heteroatom d-orbital contributions of the semi-occupied a2 orbitals in the P, As, Sb and the S, Se, Te compounds, compared to the N and O compounds. The trends in the case of B1 anionic states are the same, however, due to symmetry reasons the heteroatom perturbs the b1 orbitals more significantly than the a2 orbitals [5].

[1] A. E. Reed, P. v. R. Schleyer, J. Am. Chem. Soc., 112, 1434 (1990); E. Magnusson, J. Am. Chem. Soc., 115, 1051 (1993)
[2] C. Batich, E. Heilbronner, V. Hornung, A. J. Ashe III., D. T. Clark, U. T. Cobley, D. Kilcast, I. Scanlan, J. Am. Chem. Soc., 95, 928 (1973)
[3] P. D. Burrow, A. J. Ashe III, D. J. Bellville, K. D. Jordan, J. Am. Chem. Soc., 104, 425 (1982)
[4] D. J. Tozer, F. De Proft, J. Chem. Phys., 127, 034108 (2007)
[5] B. Hajgató, F. De Proft, D. Szieberth, D. J. Tozer, M. S. Deleuze, P. Geerlings, L. Nyulászi.
Phys. Chem. Chem. Phys., 13, 1663 (2011)

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